A new thought for twins - Compound Turbos? Maybe?

[dudemaaan]

So here's the deal, Most of you that have read my sig know what I've accomplished with a set of stock REW turbos.... 405 RWHP with all the squential hardware intact. I'll be on the dyno in a few days time to dial in the sequentials and get a base dyno for what I want my next project to be.

I recently acquired an FD that I have yet to pick up actually (BIG Thanks to Rico and Tray for hooking me up BIG) and the wheels have already started turning. I plan on using basically the same engine that I have now. A ported, polished, portmatched 13B-RE with various RX8 internals, stat gears, e-shaft mainly and the cosmo 9:1 rotors.

What I want to do is simple, beat the twins that I have now. This is easy in top end performance, but really lacks in the low end. This is where I need the most help. This is a street/auto-x/track day car. I drive my FC every nice day that I can and it honestly is a blast to drive. Non-sequentially it lacks but when I run them sequentially, she's an entirely different car. God willing I'll have the dyno sheets Tuesday and I'll post them up for sure so we (NoDOCH) can start doing some math

This setup will be in an FD and I would like to see 450-500whp and a fairly flat torque curve. Reasons for the goal, FD has better suspension, can fit wider tires, she's heavier, and frankly, I want to outdo myself.

I've been doing alot of research on the evil forum, when IB decides to let it work & I've seen a few things that jump out at me. Howard Colemans twin setup, Jason @ RX7Stores setup, A guy named Marcel Burnett (that used way oversized turbo's) and that's really it. Howards setup is everything that it claims to be. It makes 507 RWHP on pump/AI, there isvirtually nill as far as EMAP (something the stocktwins cant boast+) the turbo's aren't working all that hard, and the entire system sees pretty reliable for what it is. What I don't like about Howards setup is the fact that if you look at the dyn chart, it looks like every other single turbo chart out there. This is not what I want to see.

Jasons setup, well, it was never really finished. I thought it had potential based on the ONLY dyno sheet that was posted. It seemed like a good idea, good turbo choice (same one I was looking at for the most part, there are a ton of variants in the GT28 family) but the packaging was just aweful in my eyes. It looked rushed to me. There was little thought put into the intake plumbing to the turbo's, or from the turbo's to the intercooler. The exhaust mani was not equal length, or even close to it for that matter. I give him credit for going against the grain and trying it out, I understand he is trying to run a business, but at the same time I believe that system left alot on the table. I'm not going to let that "failure" discourage me.

Then I saw something interesting in a diesel application - compound turbo's. Aurura Turbo has a few kits' out for the diesels that are rather interesting. Basically there are two turbos of different size. The smaller turbo pulls it's air from the compressor housing of the larger turbo. Think about that as one of my questions is directly related to it. The exhaust is first routed through the smaller turbo and then to the larger turbo. All the exhaust passes through the smaller turbo before it enters the larger turbo.

This seems like a great idea. The way I see it, the smaller turbo is compressing a small amount of vaccuumed air becuase it has to pull through the larger turbo until it spools ever so slightly. However, once that larger turbo is spooling and creating positive pressure.... is that smaller turbo going to create resistance? Or is it going to further compress the charge air?

Looking at the dyno results of this system is impressive and appealing. It is EXACTELY what I'm looking for. Torque builds fast, and stays constant. Now, is this a function of the turbo's? Or the unique characteristics of the diesel engine?

I would like input on this. I am dead set on upping the ante with my FD build in terms of power. I would like to see a sequential looking torque curve that builds quickly to 360ish and holds there throughout the RPM band.

There will be no factory style exhaust mani's. I believe that is the limitation of the FDs turbo's. It's really a mess in there and it doesn't matter if I'm making 10 lbs or 14+ lbs, the EMAP is pretty much the same at around 280-290 kpa at redline. There is a direct almost perfect 1:1 ratio as boost builds. Once boost target is met though, the EMAP continues to climb. There is just too much exhaust flow and it can't effeiciently be routed out. Anyone that has seen the stock mani will understand why. In Daves words, Yeah man, it's a fucking mess in there.

So ideas and thoughts, lets here them. This will take a year if not more to come to fruition, and I don't expect any hard data until 2011 @ the earliest but mark my words, something will happen.

[TitaniumTT]

So here's the deal, Most of you that have read my sig know what I've accomplished with a set of stock REW turbos.... 405 RWHP with all the squential hardware intact. I'll be on the dyno in a few days time to dial in the sequentials and get a base dyno for what I want my next project to be.

I recently acquired an FD that I have yet to pick up actually (BIG Thanks to Rico and Tray for hooking me up BIG) and the wheels have already started turning. I plan on using basically the same engine that I have now. A ported, polished, portmatched 13B-RE with various RX8 internals, stat gears, e-shaft mainly and the cosmo 9:1 rotors.

What I want to do is simple, beat the twins that I have now. This is easy in top end performance, but really lacks in the low end. This is where I need the most help. This is a street/auto-x/track day car. I drive my FC every nice day that I can and it honestly is a blast to drive. Non-sequentially it lacks but when I run them sequentially, she's an entirely different car. God willing I'll have the dyno sheets Tuesday and I'll post them up for sure so we (NoDOCH) can start doing some math

This setup will be in an FD and I would like to see 450-500whp and a fairly flat torque curve. Reasons for the goal, FD has better suspension, can fit wider tires, she's heavier, and frankly, I want to outdo myself.

I've been doing alot of research on the evil forum, when IB decides to let it work & I've seen a few things that jump out at me. Howard Colemans twin setup, Jason @ RX7Stores setup, A guy named Marcel Burnett (that used way oversized turbo's) and that's really it. Howards setup is everything that it claims to be. It makes 507 RWHP on pump/AI, there isvirtually nill as far as EMAP (something the stocktwins cant boast+) the turbo's aren't working all that hard, and the entire system sees pretty reliable for what it is. What I don't like about Howards setup is the fact that if you look at the dyn chart, it looks like every other single turbo chart out there. This is not what I want to see.

Jasons setup, well, it was never really finished. I thought it had potential based on the ONLY dyno sheet that was posted. It seemed like a good idea, good turbo choice (same one I was looking at for the most part, there are a ton of variants in the GT28 family) but the packaging was just aweful in my eyes. It looked rushed to me. There was little thought put into the intake plumbing to the turbo's, or from the turbo's to the intercooler. The exhaust mani was not equal length, or even close to it for that matter. I give him credit for going against the grain and trying it out, I understand he is trying to run a business, but at the same time I believe that system left alot on the table. I'm not going to let that "failure" discourage me.

Then I saw something interesting in a diesel application - compound turbo's. Aurura Turbo has a few kits' out for the diesels that are rather interesting. Basically there are two turbos of different size. The smaller turbo pulls it's air from the compressor housing of the larger turbo. Think about that as one of my questions is directly related to it. The exhaust is first routed through the smaller turbo and then to the larger turbo. All the exhaust passes through the smaller turbo before it enters the larger turbo.

This seems like a great idea. The way I see it, the smaller turbo is compressing a small amount of vaccuumed air becuase it has to pull through the larger turbo until it spools ever so slightly. However, once that larger turbo is spooling and creating positive pressure.... is that smaller turbo going to create resistance? Or is it going to further compress the charge air?

Looking at the dyno results of this system is impressive and appealing. It is EXACTELY what I'm looking for. Torque builds fast, and stays constant. Now, is this a function of the turbo's? Or the unique characteristics of the diesel engine?

I would like input on this. I am dead set on upping the ante with my FD build in terms of power. I would like to see a sequential looking torque curve that builds quickly to 360ish and holds there throughout the RPM band.

There will be no factory style exhaust mani's. I believe that is the limitation of the FDs turbo's. It's really a mess in there and it doesn't matter if I'm making 10 lbs or 14+ lbs, the EMAP is pretty much the same at around 280-290 kpa at redline. There is a direct almost perfect 1:1 ratio as boost builds. Once boost target is met though, the EMAP continues to climb. There is just too much exhaust flow and it can't effeiciently be routed out. Anyone that has seen the stock mani will understand why. In Daves words, Yeah man, it's a fucking mess in there.

So ideas and thoughts, lets here them. This will take a year if not more to come to fruition, and I don't expect any hard data until 2011 @ the earliest but mark my words, something will happen.